Standard head suspension assemblies (HSAs) include, as component elements, a base plate, a load beam, a gimballing flexure and a head slider. The base plate is attached to a proximal end of the load beam, and is configured for mounting the load beam to an actuator arm of a disk drive. The flexure is positioned on a distal end of the load beam.
A style of flexure, sometimes referred to as a "T-type" or a Watrous gimballing flexure, generally includes a pair of outer flexible arms about a central aperture with a cross piece extending across and connecting the arms at a distal end of the flexure. A flexure tongue is joined to the cross piece, offset toward the attached head slider, and extends from the cross piece into the aperture. A free end of the tongue is centrally located between the flexible arms. Mounted to the free end of the flexure tongue is a head slider. The head slider must be mounted to the flexure tongue so that the head slider is in a predetermined (e.g., planar and parallel) relationship to the confronting disk surface.
Hutchinson Technology Inc. (HTI), assignee of the present invention, makes commercially available a suspension assembly, identified as the Type 13, which uses a style of flexure described above as a "T-type" or Watrous flexure. The Type 13 flexure, as is conventional with a "T-type" or Watrous flexure, is attached to a distal end of the head slider. When the disk drive using this style of flexure is moved, as in shipping or handling, or is subjected to high shock impacts, as in jarring or dropping, the head slider leaves the disk under a high "G" shock load. Recent testing has shown that, during an initial shock impact to the disk drive, the read-write head remains relatively stable with the suspension during movement away from the disk. Upon returning to the disk from this initial impact, the head strikes the disk at a relatively flat angle. When the suspension and the head rebound after this first excursion away from and .back to the disk, the suspension pulls away from the disk, pulling away the head at the end by which the head is attached to the slider. The suspension and the head are thus disoriented or dislocated from their pre-set parallel planar synchronization. The head now strikes the disk at a sharp angle upon returning to the disk surface. This sharp angle striking continues on future excursions of the suspension and head away from and back to the disk surface. These repeated sudden impacts at a sharp angle continue to damage the disk, the head slider, and/or the flexure.
It is thus desirable to reduce or eliminate the possibility of damage to the flexure, to the head slider, or to the disk by constraining or limiting the range of motion, particularly vertical motion, of the flexure relative to the load beam. Certain devices have previously been proposed to limit the range of flexure motion.
U.S. Pat. No. 4,939,611, Connolly, issued Jul. 3, 1990 and entitled VERTICAL DISPLACEMENT LIMIT STOP IN A DISK DRIVE FOR PREVENTING DISK SURFACE DAMAGE, describes a member on a comb structure of either a rotary or linear actuator for limiting vertical displacement of an arm with a confronting disk surface, such as when the disk drive is being handled for removal, installation or transportation. These vertical displacement stops are located outside of tracks recorded on the disk, so that they do not interfere with the function of any disk drive parts during periods of normal operation. However, this displacement stop is designed for use only during non-operational periods and does not provide protection to limit flexure motion when the disk drive is in normal operation.
U.S. Pat. No. 4,724,500, Dalziel, issued Feb. 9, 1988 and entitled MECHANISM FOR PREVENTING SHOCK DAMAGE TO HEAD SLIDER ASSEMBLIES AND DISKS IN RIGID DISK DRIVE, describes an elongated constraint element positioned on the side of the load beam opposite the flexure, in association with a pair of wing elements attached to shoulder extensions of the head slider. The constraint element and the wing elements, together with the specially configured head slider, serve to limit the range of motion, both vertical and rotational, of the flexure tongue. The Dalziel structure is rather complicated, adding significantly to the weight, height and difficulty of manufacture and assembly of the suspension.
Accordingly, there continues to be a need to limit the range of motion of the flexure tongue and the attached head slider relative to the load beam under both operational and non-operational drive modes, without unduly adding to the structure of the suspension assembly.